1. Field of the Invention
The invention relates to a selvage-forming device for a power loom, with yarn guide structures to raise and lower at least two selvage yarns.
2. Related Art
Selvage-forming devices cooperating with selvage yarns are used in looms to form a fabric selvage or a waste band. The selvage yarns are guided in yarn guide structures which raise and lower these yarns to subtend sheds in which the fillings are laced into the selvage yarns in a predetermined pattern. The yarn guide structures usually are fitted with yarn guide elements in the form of circular, oval or slotted apertures. The selvage yarns also are called catch threads.
Selvage-forming devices for at least two selvage yarns are known. Therein a first selvage yarn is moved up and down in one plane while a second selvage yarn is moved up and down in the opposite direction to the first one and simultaneously is displaced transversely to the plane of the up-and-down motion, whereby the two selvage yarns cross each other.
The known selvage-yarn devices contain a needle moving in a plane and comprising an eye guiding a first selvage yarn. Moreover they contain two yarn guide structures fitted with crossed slots to guide a second selvage yarn and which are displaced oppositely to the needle. In the process the yarn guide structures with the crossed slots also move relative to each other, and, because of the relative displacement of the slots, the second selvage yarn is shifted perpendicularly to the above-mentioned plane, and as a result the two selvage yarns will cross.
Such a selvage-forming device is described in U.S. Pat. No. 4,478,256. The selvage-forming device is driven jointly with the loom's harnesses. Accordingly this selvage-forming device only allows interlacings, i.e. weaves, which are determined by the paths of the harnesses. Another selvage-forming device is disclosed in U.S. Pat. No. 3,171,443 and is driven by the same drive elements of the loom drive system. The drive is fairly complex. A change in interlacing is possible only after substantial labor.
The object of the invention is to create a selvage-forming device of the type discussed above that allows changing in a simple manner the weave of selvage yarns and fillings. cl Summary of the Invention
This problem is solved by providing an independently controlled drive to raise and lower the selvage yarns in a mutually opposite manner by means of eccentric drives that are connected to the linearly guided yarn guide structure. The yarn guide structures of at least one selvage yarn implement the crossing of this selvage yarn while it is being raised and lowered with another selvage yarn transversely to the direction of raising and lowering. The motion of the yarn guide structure required to cross the at least one selvage yarn is derived from the eccentric drive associated with said selvage yarn.
The invention makes it possible to change the weave of selvage yarns and inserted fillings in a simple manner in the case of consecutive filling insertions because only the drive control need be changed. As regards consecutive insertions of fillings, the number of fillings interlaced with the selvage yarns and/or the kind of mutual crossing of selvage yarns can easily be changed.
A selvage-forming device according to the invention offers the advantage of being highly compact and constituted of few parts. It can be implemented in modular form. Moreover it can be installed and disassembled in a simple manner and furthermore it can be shifted width-wise of the power loom when the fabric width is changed.